1) Field of the Invention
The present invention relates to an aromatic polyester resin composition and fiber. More particularly, the present invention relates to an aromatic polyester composition having an extremely durable antistatic property, sweat-absorbing property, soil-releasing property and hydrophilic property, which is useful for the production of shaped articles such as a fiber, film and sheet, and to a fiber made therefrom.
2) Description of the Related Arts
An aromatic polyester resin has many excellent characteristics, and therefore, the resin is used as a material for the production of shaped articles such as a fiber, a film and a sheet. But since the aromatic polyester resin is hydrophobic, the use of the aromatic polyester resin in fields where hydrophilic characteristics such as an antistatic property, sweat-absorbing property and soil-releasing property are required is restricted.
Attempts have been made to impart hydrophilic characteristics to the aromatic polyester resins, to manifest such functions as an antistatic property, sweat-absorbing property and soil-releasing property, and many proposals have been made to this end. As one attempt to impart antistatic characteristics to a polyester fiber, a method is known which comprises incorporating a polyoxyalkylene glycol into a polyester (see, for example, Japanese Examined Patent Publication No. 39-5214). In this method, however, to impart a sufficient antistatic property to the polyester fiber, it is necessary to add a polyoxyalkylene glycol in a large amount such as 15 to 20% by weight, and therefore, the physical properties, especially thermal properties, of the resultant antistatic polyester fiber are greatly lowered and the washing fastness is poor. Accordingly, this antistatic polyester fiber cannot be put to practical use.
As the means for overcoming this defect, a method is known which comprises the steps of mixing, a polyester resin with a polyoxyalkylene glycol, a polyoxyalkylene glycol/polyamide block copolymer or a polyoxyalkylene glycol/polyester block copolymer, which is substantially incompatible with the polyester resin, and further mixing with an organic or inorganic ionic compound (see, for example, Japanese Examined Patent Publication No. 44-31828, Japanese Examined Patent Publication No. 60-11944, Japanese Unexamined Patent Publication No. 53-80497 and Japanese Unexamined Patent Publication No. 60-39413). According to this method, the total amount of the antistatic agent to be used can be reduced, and therefore, an antistatic polyester, in which the reduction of the physical properties is relatively small, can be obtained. Nevertheless, the antistatic polyester fiber obtained according to this method is defective in that the chemical performance, for example, color fastness thereof, is easily lost. Furthermore, if this polyester fiber is subjected to a weight-reducing alkali treatment usually conducted for improving the touch, especially a weight-reducing treatment where the weight-reducing ratio is at least 20% by weight, which is necessary for manifestation of a silk-like touch, the antistatic property thereof is easily lost at the subsequent dyeing step usually conducted at a temperature of 120.degree. to 135.degree. C. Accordingly, this polyester fiber cannot be practically used in fields where an antistatic property is required.
Furthermore, there has been attempted a method in which a polyester resin composition containing a small amount (3% by weight at largest) of an antistatic agent substantially incompatible with the polyester resin, and consisting of a polyoxyalkylene glycol and a metal salt of sulfonic acid, is melt-spun into a hollow fiber, whereby the majority of the added antistatic agent is concentrated and predominantly distributed in the inside surface portion around the hollow of the hollow fiber and it is possible to improve the touch by a weight-reducing alkali treatment (see Japanese Examined Patent Publication No. 60-56802). To impart sufficient antistatic characteristics to a polyester fiber according to this method, however, it is necessary to strictly control the fiber-forming conditions and the like and restrict the bleed-out of the antistatic agent to the inside surface portion around the hollow of the hollow fiber. This necessity results in that the fiber-producing cost is increased. Furthermore, if this polyester fiber is subjected to a weight-reducing alkali treatment and the weight of the fiber is reduced to at least 15% by weight, the imparted antistatic characteristics of the fiber are easily lost in the subsequent dyeing operation. Moreover, this polyester fiber is defective in that, since the fiber has the hollow portion, when this polyester is dyed the color depth or color vividity of the resultant dyed fiber is unsatisfactory.
Separately, in a core-in-sheath type conjugate fiber, it has been attempted to distribute an antistatic agent at a high concentration predominantly in a core portion of the core-in-sheath type conjugate fiber and to render a weight-reducing alkali treatment possible (see, for example, Japanese Examined Patent Publication No. 61-6883, Japanese Unexamined Patent Publication No. 55-122020 and Japanese Unexamined Patent Publication No. 61-28016). But this fiber is a conjugate fiber, and thus is defective in that the fiber-producing cost is drastically increased. Moreover, the antistatic property of the resultant fiber is unsatisfactory.
Furthermore, an antistatic resinous composition comprising about 3 to 30% by weight of a high molecular weight ethylene oxide copolymer having an average molecular weight of 20,000 or more and 70 to 97% by weight of a high molecular material is disclosed by Japanese Unexamined Patent Publication No. 64-26674. This Japanese publication discloses that propylene oxide and 1,2-dodecylene oxide are usable as a comonomer to be copolymerized with the ethylene oxide.
In this attempt, since the high molecular weight ethylene oxide copolymer is utilized as a antistatic agent, when this is applied to the aromatic polyester resin, the bleed out of the antistatic agent is restricted, and accordingly the resultant aromatic polyester resin composition does not exhibit a satisfactory initial antistatic property.
Also, the ethylene oxide copolymers specifically disclosed in the Japanese publication are all random copolymers and water-soluble or water-dispersible, and therefore, when the ethylene oxide copolymers are utilized to produce fibers, the resultant fibers exhibit a poor resistance to hot water, alkali and laundering, and an unsatisfactory durability of the antistatic property, and thus cannot be practically employed.
Furthermore, other attempts have been made to impart hydrophilic characteristics such as an antistatic property, sweat-absorbing property, and soil-releasing property by a finishing treatment. For example, there are known a method comprising applying a hydrophilic polymeric compound to the surface of a fiber (see, for example, Japanese Examined Patent Publication No. 53-47437), and a method comprising polymerizing a polymerizable monomer having a hydrophilic group on the surface of a fiber to form a coating (see, for example, Japanese Unexamined Patent Publication No. 53-130396). If hydrophilic fibers obtained according to these methods are repeatedly subjected to a severe washing treatment, however, the imparted effects are often lost, and if the amount of treating agent applied is increased to improve the durability of the hydrophilic characteristics, the touch of the resultant fiber becomes coarse and rigid and the color fastness becomes poor. For examples, when a polyester fiber is used for a thin woven fabric useful for, for example, a dress or blouse for which a soft touch is required, the polyester fiber is frequently subjected to a weight-reducing treatment with an alkali. If the polyester fiber, which has been subjected to the weight-reducing alkali treatment, is subjected to the above-mentioned finishing treatment, a problem arises in that the durability of the resultant treatment effect becomes poor.
As apparent from the foregoing description, a solid nonhollow, non-conjugate type fiber made of an antistatic polyester resin, which is modified so that the fiber can endure a weight-reducing alkali treatment resulting in a large reduction of the weight, is not presently available. Moreover, the finishing treatment technique is limited, and therefore, development of an antistatic polyester solid fiber capable of enduring a severe weight-reducing alkali treatment causing a weight reduction of at least 20% by weight, which is necessary for improving the touch, is urgently required.
As the means for imparting a water-absorbing property (the capacity of absorbing water in the liquid state) to a polyester fiber, there have been proposed the above-mentioned method comprising forming a hydrophilic coating film on the surface of a polyester fiber, and a method comprising subjecting a polyester fiber to an electric discharge treatment, a method comprising graft-polymerizing a hydrophilic compound such as acrylic acid or methacrylic acid to a polyester fiber, and a method comprising etching the surface of a polyester fiber with a chemical. Moreover, there has been attempted a method in which a polyester fiber is rendered porous and the water-absorbing property thereof is improved by utilizing the capillary phenomenon thereof.
Many investigations have been made into methods of imparting a moisture-absorbing property (the capacity of absorbing water in the vapor state), for example, the above-mentioned method in which the polyester is copolymerized with a polyoxyalkylene glycol, but the effect of improving the moisture-absorbing property by the copolymerization with a polyoxyalkylene glycol is poor and the reduction in the heat resistance and light resistance is conspicuous, and therefore, a product that can be practically used is not obtained. A moisture-absorbing polyester fiber having a moisture absorption comparable to that of cotton, which is prepared by graft-polymerizing acrylic acid or methacrylic acid to a polyester fiber and converting the grafted component to a sodium salt thereof, has bean attempted, but this type of polyester fiber is defective in that the moisture-absorbing property thereof is easily lost by washing, the reduction in the color fastness thereof is conspicuous, and the touch becomes hard. Accordingly, this type of polyester fiber cannot be put to practical use.
Moreover, there has been attempted a method in which a moisture-absorbing polyester fiber having a porous structure and exhibiting a capillary condensing action is formed by steam-drawing an undrawn fiber of a polyester resin containing a specific oxalic acid complex salt incorporated therein (see Japanese Unexamined Patent Publication No. 54-93121), but since the oxalic acid complex salt is easily soluble in water, if this polyester fiber is subjected to high-pressure dyeing or washing procedure, the moisture-absorbing property of the fiber is easily lost, and thus this type of polyester fiber cannot be put to practical use.
In view of the importance of the capillary condensation type of polyester fiber, we have heretofore made several approaches concerning moisture-absorbing polyester fibers (see Japanese Unexamined Patent Publication No. 60-155770, Japanese Unexamined Patent Publication No. 60-167969, Japanese Unexamined Patent Publication No. 61-215770 and Japanese Unexamined Patent Publication No. 61-231221 ). In the capillary condensation type of moisture-absorbing polyester fibers, however, since fine pore-forming agents contained in these fibers are water-soluble, a reduction of the moisture-absorbing property by a high-pressure dyeing or washing procedure cannot be avoided. Accordingly, development of the capillary condensation type of a moisture-absorbing polyester fiber having a high durability to high-pressure dyeing and laundering is urgently required.
The inventors of the present invention have made an attempt to provide a hydrophilic polyester fiber having excellent mechanical properties, alkali resistance and laundering resistance, by replacing the water-soluble polyoxyethylene glycol conventionally used to provide antistatic polyester fibers by a water-insoluble polyoxyethylene polyether polymer which is a copolymerization product of ethylene oxide with a specific higher olefin oxide.
Nevertheless, it was found that the above-mentioned type of antistatic polyester fibers are not satisfactory in that, when the antistatic polyester fibers were subjected to an alkali treatment with a weight reduction of 20% or more, and-then to a 30 times laundering treatment, it is difficult for the treated polyester fibers to satisfy all of the requirements of a high durability of the antistatic property, dyeing property evaluated by naked eye observation, and abrasion resistance.
In the above-mentioned attempt, the durability of the antistatic property of the polyester fiber was tested in such a manner that one test cycle consisting of one laundering treatment and one heat treatment at a temperature of 170.degree. C. for one minute, and this cycle was repeated to a predetermined number of times. In this test method, the polyoxyethylene polyether polymer is bled-out from the inside to the surface of the fiber during the heat treatment, and therefore, the evaluated durability of the antistatic property of the polyester fiber in appeared to be better than that evaluated by another test method in which no heat-treatment but only the laundering treatment is applied.
The antistatic polyester fibers, which can be subjected to a weight-reduction treatment with alkali, are mainly used for lining fabric and lingerie. In this use, the polyester fiber fabric is not always heat treated after the laundering treatment. Therefore, sometimes the above-mentioned polyester fiber fabric cannot exhibit a satisfactory antistatic property, due to the lack of bleed-out of the antistatic agent.
Accordingly, there is a need to provide a polyester fiber which exhibits a satisfactory antistatic property even when the fiber is not heat treated, and a high durability of the antistatic property.